Many telephones currently used in both the home and/or the office require AC power to operate. Such AC powered phones cannot derive dial tone if AC power is not present. Examples of such phones include cordless phones with an AC powered local base station, advanced feature phones including displays and accommodating such options as caller identification (ID), phones integrated with other devices, such as e.g., automated answering and/or automated call machines, and Internet Protocol (IP) phones. As consumers and industry have embraced these new AC powered phones, in many cases, these new AC powered phones have replaced older equipment, e.g., standard plain old telephone service (POTS) phones which are powered via a landline telephone line coupled to a Central Office and did not require an AC power source to operate. In many cases, a home or an office no longer has any standard POTS phones and now uses solely AC powered phones.
In the event of a power failure, e.g., due to a downed power line or transformer from a storm, due to a power station shutdown, or due to a terrorist act, homes or businesses using AC powered phones would be unable to make any calls out of or receive any calls into the residence or business, even though, in many cases, the landline phone lines to the residence or business would be still intact and fully operational.
Although many individuals now carry a personal cell phone, the cellular networks have limited capacity. In times of emergency, the number of individuals attempting to use their cell phones simultaneously may, and in many cases does, exceed the capacity, resulting in many individuals being unable to complete a call. In addition, cell phones coverage varies as a function of location. Cell phone coverage in offices and buildings is limited due to the problems associated with signal propagation. Individuals, e.g., trapped in a building, may be in a location of poor reception such as the interior of a building and be unable to complete a cell phone call. Also, in many instances, the cell tower and/or cell base station may have also lost power, rendering the cell phones within that cell useless.
Cell phones operate on batteries with limited energy storage capacity and require frequent recharges using AC power or battery replacement. In times of an extended local AC power outage, many cell phones may become inoperative due to depleted batteries.
In view of the above mentioned problems, it would be advantageous if cordless phones, e.g., cell phones, included a capability to function as a conventional POTS phone, requiring no AC power. It would be advantages if such multi-mode phones included battery monitoring capabilities and provided users with different options, e.g., options requiring no battery power and options using battery power and perhaps providing additional advanced capabilities.